Method of purifying metals



April 10, 1928.

J. J. CONLIN METHOD OF PLRIFYING METALS Filed April .6. 1927 lnventof: John J. Conlin,

His Attorney.

Patented Apr.` 10, 1928.

UNITED\ STATES ,665,s44 PATENT OFFICE.

JOHN J. CONLIN, OF SCHENECTDY, NEW YORK, ASSIGNOR TO GENERAL ELECTBC COMPANY, A COR'PORATION OF NEW YORK.

METEO:) OF PURIFYING mmm Application filed April 6, 1927. Serial No. 181543.

The present invention relates to the purification of metals and more particularly to the purification of metals of the alkah or 1 alkaline earth groups. Certain of these metals, particularly calcium and magnesum, are frequently employed as getters in Vacuum tube Construction. 'They are readly oxidizable and normally contain 'a considerable percentage of impurities, usually inthe. form of salts, which it 'is desirable to re move before' themetal is introduced into vacuum tubes. 7 i It is one of the objects of the present invention to 'provide a simple-and inexpensve process for the removal of such included salts. It is a further object of the invention to provide a method for forming an alloy o--a lura-lity of such metals at the 'same time t h from. I\ i Y I The novel features which I believe' to be characteristic of my invention are set forth in the appended clams. My invention itself, however, will best be understood from reference to the following specification when taken in connection with the accompanying drawing in which the single figure shows a cross section of an apparatus whereby my invention may be carred into eflect;

Referring to the drawing, I have indicated 'at 1 a suitable furnace having a burner 2 located adjacent the lower end thereof, the burner being supplied with gas and air through pipes3 and 4 respectively. An open metallic container 5 partially filled with a suitable salt, such as calcium chloride, is mounted in the furnace so that the flames from the burner may be directed around the lower end thereof. Calcium is inserted into a steel tube 6 which is about 2 inches in diameter and 9 inches long. The upper end of the tube is closed by a' plug 7 and pro vided with an elongated handle 8. A metal plug 9 approximately f 'inch in thickness and having a small opening 10 is detachably Secured by a bolt or screws 11 at the lower end of the tube.

In operation the calcium chloride is gradually heated up to a temperature of about i 900 C. When the temperature has been raised to about 800 C., the steel tube 6 containing the calcium is immersed to a slight extent in`the salt and as the temperature of v the latter is raised the tube ie gradually lowered into the salt. When the upper tem- 'attheimpurities are removed thereperature limit 900 C. has been reached the tube is entirely submerged andheld in this poston for about fiveminutes. The entire operation consumes approximately twenty mnutes. Substantially pure calcium floats to the top of the tube, while the calcium salts sink to the bottom. There is a sharp line of demarcation between the calcium and the salts and the lattermay be easily separated from the-calcium by'removing plug 9 and 'cutting the tube 6 lengthwise.

The opening 10 acts as a safety valve and prevents the pressure in tube 6 from rising too high; Although a small amount of calcium salt enters tube 6 through this opening, this action does not' interfere with *the operation of the process since the salt which enters remains at the bottom of the tube. i

The same process may be employed with other oxidizable metals, such as magnesium. '(5 Furthermore, other salts than calcium chloride may be employed if desired, the main consideration for such salts being that they should not be volatile at 900 C. and should not react with the metal which it is desired to purify. i The process may also be employed to simultaneously purify a lurality of metals and to form an alloy o the metals at the same time that the impurities are removed. .85 For exam le, 'if magnesium is placed in the upper par of tube 6 and calcium in the lower part, and the tube then immersed in molten calcium chloride as above described, the included saltsin the calcium and magnesium oo will sink to the bottom of the tube while the magnesium and calcium will rise above the salts and form a substantiall pure alloy that is particularly adaptable or use as a getter in vacuum tubes.

What I claim 'as new and desire to secure by Letters Patent of the United States, is

1.- The method of purifying a readily oxidizable metal which comprses placing the metal in a container provided with a on I vent and submerg'ing the container in molten material which does not react with said metal and which has a temperature suificintly high to cause separation of the metal and impurities contained therein.

2. The method of treating a readily oxidizable `metal which comprises placing it in a rigid container having an opening in the lower portion thereof and immersing the container in a molten salt which does not o react with said metal and which has a temperature sufliciently high to cause separation of the metal and mpurities contain'ed therein.

3. The method of purifying a readily exidizable metal which comprises placing the metal in a container ha vmg an opening in the lower end thereofmd immersing the container in a salt which does not react with the said metal and which has a temperature sufliciently high to cause separation of the metal and impurities contained therein.

- 4. The method of preparing a substantially pure alloy which comprises placing the metals comprising the alloy in a container having a. vent' therein and submerg'ing the which has a temperature of about 900 C.

p In witness whereof, I have hereunt'b set my hand this 5th day of April, 1927 JOHN J. CONLIN. 

